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Cryptosporidium

Cryptosporidium parvum is a parasite which can infect the intestines and cause diarrhea. Most people with healthy immune symptoms will recover. People who have poor health or have a weakened immune system can have more severe and prolonged illness. Cryptosporidia are passed in the stools of animals, and can contaminate food, the environment and water supplies.

Information for Health Professionals

Cryptosporidium parvum is a parasite that infects the intestinal tract. When a person gets sick from this infection it is called cryptosporidiosis.

Cryptosporidiosis may result in: 

  • frequent, watery diarrhea
  • stomach cramps
  • nausea
  • vomiting
  • mild fever
  • dehydration

Symptoms start an average of 7 days (range 1-12 days) after exposure to the parasite. Often a person can be infected and have no symptoms. Symptoms usually last for 1 to 2 weeks in people who are otherwise healthy. In some cases, symptoms can return after you have started to recover. People who have poor health or have a weakened immune system can have more severe and prolonged illness.

Cryptosporidiosis is spread by the fecal-oral route. Fecal material from infected humans or animals can get into our mouths by

  • consuming contaminated food or drink
  • contact with the feces of infected humans (e.g. changing diapers) that is not followed by proper hand washing
  • contact with the feces of domestic or wild animals, including pets and farm animals, that is not followed by proper hand washing. Pets may also have fecal matter on their hair or fur that is transferred to our hands when we touch them.
  • outbreaks are usually due to contamination in a water system

Cryptosporidiosis is commonly a water-borne disease. Cryptosporidia are very hardy organisms that survive for long periods of time in the environment including in water, since they have the ability to form a hardy spore (called an oocyst).

Diarrhea can result in dehydration, especially in young children and pregnant women. Rapid loss of fluids from diarrhea may be especially life threatening to babies, who may require fluid replacement therapy.

People with poorly functioning immune systems are at risk of more serious illness when they get cryptosporidiosis (e.g. severe dehydration). They are also more at risk for prolonged illness.


Examples of people with weakened immune systems include:

  • people with HIV/AIDS;
  • those with inherited diseases that affect the immune system; and
  • cancer and transplant patients who are taking certain immunosuppressive drugs.

A microscopic examination of a stool sample will enable a diagnosis of cryptosporidiosis.

Ensuring sufficient fluid intake to prevent dehydration from diarrhea is very important, especially for young children and pregnant women.


Most people with healthy immune systems recover without treatment. Please consult your healthcare provider to discuss whether you require treatment.


Your healthcare provider may recommend you take antidiarrheal medications.


For individuals with a healthy immune system, an anti-parasitic medication may be prescribed (for patients one year of age or older).


In immunocompromised patients, an improved immune status is needed for successful treatment. For people with HIV/AIDS, anti-retroviral therapy is essential. Anti-parasitic medications are also used.

If you think you have a cryptosporidium infection, see your family doctor for testing, advice and treatment. 

Cryptosporidia are passed in the feces; therefore, people with diarrhea which may be due to an infection should not go to work or school. 

If you are a food handler or health care worker it is possible for you to transmit cryptosporidiosis to others while carrying out your duties in these settings. Do not work while you have diarrhea or vomiting and do not return to work until 48 hours after your last loose stool or episode of vomiting. This time period will ensure you have a chance to recover and lessen the possibility of transmitting the infection to others. 

Children in day care who have diarrhea can be cared for temporarily in an area separate from other children until picked up by their parents. Children cannot return to day care until 48 hours after their last loose stool or episode of vomiting. To ensure proper hand washing, children in day cares should be supervised by an adult when washing their hands. 

When you recover you may excrete cryptosporidia in your stools for several weeks and possibly infect others. After using the toilet and before eating or preparing foods, wash your hands thoroughly with liquid soap and water.

If you are immune-compromised, find out what kind of treatment your water supply has. 


Refer to the information in HealthLink BC File #56: Weakened Immune Systems and Water-borne Infections.

  • If your local drinking water providere has issued a Boil Water Notice for your community water system, take the advice seriously.
  • Do not drink untreated surface water from a spring, stream, river, lake, pond or shallow well. Assume it is contaminated with animal feces. Boil or filter water from these sources that is used for
  1. drinking
  2. making ice cubes
  3. washing uncooked fruits and vegetables
  4. making baby formula
  5. brushing teeth
  6. rinsing dentures
  7. any purpose where consumption will occur without adequate heat treatment.
  • When camping, do not relieve yourself within 100 feet of a water source.
  • If you have a cryptosporidium infection, do not swim in lakes, ponds, streams, rivers, swimming pools and hot tubs while you have diarrhea and until at least 48 hours after the diarrhea has stopped. Avoiding this activity will help to ensure that other swimmers do not become infected.
  • Do not drink unpasteurized milk or juices.
  • WASH YOUR HANDS:
    1. Before eating
    2. Before handling food
    3. After using the toilet or changing diapers
    4. After touching animals
  • Make sure children, particularly those who handle pets, wash their hands carefully before eating and on a regular basis if they suck their thumbs or put their hands in their mouths.
  • There are two methods to eliminate Cryptosporidia from water:
  1. Boiling: Bring water to a rolling boil for at least 1 minute and then allow it to cool. At elevations over 2,000 meters (6,562 feet) you should boil water for at least 2 minutes to disinfect. Boiling will not purify water that is obviously heavily polluted or chemically contaminated.
  2. Filtering: To effectively remove cryptosporidium cysts, filters must have an absolute pore size of 1 micron or be rated by the National Sanitation Foundation (NSF) for cyst removal. Cysts are 4 to 6 microns in length and will not pass through a filter pore of 1 micron. Some portable water treatment units used for camping meet the above requirements.

Jug-type water filters are not effective in removing cryptosporidia. Some built-in water filtration systems will remove cryptosporidia, but they need regular and thorough maintenance to work effectively. 

Other types of water treatment units, such as distillation units, reverse osmosis and combination (filtration and ultraviolet) units are also available. Check with local water purification suppliers or your local environmental health officer for more detailed information. 

Cryptosporidia are resistant to chlorine. Treating water with chlorine will NOT remove the parasite.


SOURCE: Cryptosporidium ( )
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